TY  - JOUR
AU  - Awad, Mahmoud E.
AU  - López-Galindo, Alberto
AU  - Medarević, Đorđe
AU  - Milenković, Marina
AU  - Ibrić, Svetlana
AU  - El-Rahmany, Mahmoud M.
AU  - Iborra, César
PY  - 2021
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/3800
AB  - The present research aims to enhance the antimicrobial activity of kaolinite surfaces by a one-step cost-effective and energy-efficient dry thermal reaction, producing an antibacterial and antifungal silver-kaolinite (Ag-Kao) nanocomposite agent. Pharmaceutical grade kaolin powder samples, with variable kaolinite structural order–disorder degree, were homogeneously mixed with silver nitrate in a proportion 1:4 AgNO3:kaolin (w/w) and sintered at 400 °C for 30 min. The composition, microstructure, microtexture and surface characteristics of the pyro-fabricated nanocomposites were characterized by XRD/XRF diffractometry, differential scanning calorimetry DSC, FT-IR spectroscopy, TEM/EDX, zeta potential (mV) measured within the 2–12 pH range, and BET method. Physicochemical stability was evaluated by silver dissociation testing under close-neutral and acidic conditions with Ag content assay using ICP-OES. The resulting Ag-Kao nanocomposites exhibited bulk silver contents ranging from 9.29% to 13.32% with high physicochemical stability in both neutral and acidic mediums (Ag dissociation rate <0.5% in 5 days). Ag nanocrystals exhibited particle sizes ranging from 5 to 30 nm, which were embedded and reinforced within the kaolinite matrix. The sizes of the Ag nanocrystals and their distribution patterns on the edges and faces of kaolinite platelets were controlled by the structural order–disorder degree. Highly ordered kaolinites (Hinckley Index, HI > 1) produced platelet edge-clustered silver nanocrystals due to the abundance of the dangling hydroxyls on platelet edges, while the highly disordered kaolinite (HI < 1) provided homogeneous platelet basal-doped silver nanocrystals due to the presence of some residual charges by exposed basal hydroxyl groups with interplatelet silver diffusivity. At pH 2, the magnitude of the positive surface charge was influenced by the silver nanocrystal size. Nanocomposites with the smallest silver nanocrystals (10–5 nm) exhibited the highest positive zeta potential (+15.2 mV to +17.0 mV), while those with larger silver nanocrystals (up to 30 nm) indicated lower positive zeta potential values (+9.5 mV to +3.6 mV). Under the same testing conditions using the Mueller-Hinton broth microdilution method, the raw kaolin samples did not show any significant antimicrobial activity, while all the pyro-fabricated Ag-Kao nanocomposite samples showed potent antibacterial and antifungal activity at low doses (MIC range 0.1–0.0125 mg/mL). Therefore, modulation of the effective electrostatic surface charge of the kaolinite platelets, via thermal doping of silver within their basal planes and edges, was found to be strongly dependent on the pH as well as the size and microtexture of the silver nanocrystals (mainly controlled by the order–disorder degree HI). The resulting modified nanostructure, with physicochemical stability and the efficient surface properties of the designed pyro-fabricated nanocomposite, led to an enhanced synergistic biophysical antimicrobial activity.
PB  - Elsevier B.V.
T2  - International Journal of Pharmaceutics
T1  - Enhanced antimicrobial activity and physicochemical stability of rapid pyro-fabricated silver-kaolinite nanocomposite
VL  - 598
DO  - 10.1016/j.ijpharm.2021.120372
ER  - 

@article{
author = "Awad, Mahmoud E. and López-Galindo, Alberto and Medarević, Đorđe and Milenković, Marina and Ibrić, Svetlana and El-Rahmany, Mahmoud M. and Iborra, César",
year = "2021",
abstract = "The present research aims to enhance the antimicrobial activity of kaolinite surfaces by a one-step cost-effective and energy-efficient dry thermal reaction, producing an antibacterial and antifungal silver-kaolinite (Ag-Kao) nanocomposite agent. Pharmaceutical grade kaolin powder samples, with variable kaolinite structural order–disorder degree, were homogeneously mixed with silver nitrate in a proportion 1:4 AgNO3:kaolin (w/w) and sintered at 400 °C for 30 min. The composition, microstructure, microtexture and surface characteristics of the pyro-fabricated nanocomposites were characterized by XRD/XRF diffractometry, differential scanning calorimetry DSC, FT-IR spectroscopy, TEM/EDX, zeta potential (mV) measured within the 2–12 pH range, and BET method. Physicochemical stability was evaluated by silver dissociation testing under close-neutral and acidic conditions with Ag content assay using ICP-OES. The resulting Ag-Kao nanocomposites exhibited bulk silver contents ranging from 9.29% to 13.32% with high physicochemical stability in both neutral and acidic mediums (Ag dissociation rate <0.5% in 5 days). Ag nanocrystals exhibited particle sizes ranging from 5 to 30 nm, which were embedded and reinforced within the kaolinite matrix. The sizes of the Ag nanocrystals and their distribution patterns on the edges and faces of kaolinite platelets were controlled by the structural order–disorder degree. Highly ordered kaolinites (Hinckley Index, HI > 1) produced platelet edge-clustered silver nanocrystals due to the abundance of the dangling hydroxyls on platelet edges, while the highly disordered kaolinite (HI < 1) provided homogeneous platelet basal-doped silver nanocrystals due to the presence of some residual charges by exposed basal hydroxyl groups with interplatelet silver diffusivity. At pH 2, the magnitude of the positive surface charge was influenced by the silver nanocrystal size. Nanocomposites with the smallest silver nanocrystals (10–5 nm) exhibited the highest positive zeta potential (+15.2 mV to +17.0 mV), while those with larger silver nanocrystals (up to 30 nm) indicated lower positive zeta potential values (+9.5 mV to +3.6 mV). Under the same testing conditions using the Mueller-Hinton broth microdilution method, the raw kaolin samples did not show any significant antimicrobial activity, while all the pyro-fabricated Ag-Kao nanocomposite samples showed potent antibacterial and antifungal activity at low doses (MIC range 0.1–0.0125 mg/mL). Therefore, modulation of the effective electrostatic surface charge of the kaolinite platelets, via thermal doping of silver within their basal planes and edges, was found to be strongly dependent on the pH as well as the size and microtexture of the silver nanocrystals (mainly controlled by the order–disorder degree HI). The resulting modified nanostructure, with physicochemical stability and the efficient surface properties of the designed pyro-fabricated nanocomposite, led to an enhanced synergistic biophysical antimicrobial activity.",
publisher = "Elsevier B.V.",
journal = "International Journal of Pharmaceutics",
title = "Enhanced antimicrobial activity and physicochemical stability of rapid pyro-fabricated silver-kaolinite nanocomposite",
volume = "598",
doi = "10.1016/j.ijpharm.2021.120372"
}

Awad, M. E., López-Galindo, A., Medarević, Đ., Milenković, M., Ibrić, S., El-Rahmany, M. M.,& Iborra, C.. (2021). Enhanced antimicrobial activity and physicochemical stability of rapid pyro-fabricated silver-kaolinite nanocomposite. in International Journal of Pharmaceutics
Elsevier B.V.., 598.
https://doi.org/10.1016/j.ijpharm.2021.120372

Awad ME, López-Galindo A, Medarević Đ, Milenković M, Ibrić S, El-Rahmany MM, Iborra C. Enhanced antimicrobial activity and physicochemical stability of rapid pyro-fabricated silver-kaolinite nanocomposite. in International Journal of Pharmaceutics. 2021;598.
doi:10.1016/j.ijpharm.2021.120372 .

Awad, Mahmoud E., López-Galindo, Alberto, Medarević, Đorđe, Milenković, Marina, Ibrić, Svetlana, El-Rahmany, Mahmoud M., Iborra, César, "Enhanced antimicrobial activity and physicochemical stability of rapid pyro-fabricated silver-kaolinite nanocomposite" in International Journal of Pharmaceutics, 598 (2021),
https://doi.org/10.1016/j.ijpharm.2021.120372 . .

TY  - JOUR
AU  - Awad, Mahmoud E.
AU  - López-Galindo, Alberto
AU  - Medarević, Đorđe
AU  - Đuriš, Jelena
AU  - El-Rahmany, Mahmoud M.
AU  - Ibrić, Svetlana
AU  - Viseras, César
PY  - 2020
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/3496
AB  - The present work aimed at assessing the pharmaceutical tableting properties of some Egyptian kaolin samples belong to the Abu Zenima kaolin deposits (estimated at 120 million tons). Four representative samples were selected based on kaolinite richness and their structural order-disorder degree, and after purification, they were dried at 70 C and heated from room temperature up to 400 C (10 C/min). Mineralogy, micromorphology, microtexture, granulometry, porosimetry, moisture content, bulk and tapped density, direct and indirect flowability, and tableting characteristics are studied. Results indicated that purified kaolin samples were made up of 95–99% kaolinite, <3% illite, 1% quartz and 1% anatase. The powder showed mesoporous character (pore diameters from 2 to 38 nm and total pore volume from 0.064 to 0.136 cm3/g) with dominance of fine nanosized particles (<1 m–10 nm). The powder flow characteristics of both the ordered (Hinckley Index HI > 0.7, crystallite size D001 > 30 nm) and disordered (HI < 0.7, D001 < 30 nm) kaolinite-rich samples have been improved (Hausner ratio between 1.24 and 1.09) as their densities were influenced by thermal treatment (with some observed changes in the kaolinite XRD reflection profiles) and by moisture content (variable between 2.98% and 5.82%). The obtained tablets exhibited hardness between 33 and 44 N only from the dehydrated powders at 400 C, with elastic recovery (ER) between 21.74% and 25.61%, ejection stress (ES) between 7.85 and 11.45 MPa and tensile fracture stress (TFS) between 1.85 and 2.32 MPa, which are strongly correlated with crystallinity (HI) and flowability (HR) parameters. These findings on quality indicators showed the promising pharmaceutical tabletability of the studied Egyptian kaolin powders and the optimization factors for their manufacturability and compactability.
PB  - MDPI
T2  - Minerals
T1  - Flow and tableting behaviors of some egyptian kaolin powders as potential pharmaceutical excipients
VL  - 10
IS  - 1
DO  - 10.3390/min10010023
ER  - 

@article{
author = "Awad, Mahmoud E. and López-Galindo, Alberto and Medarević, Đorđe and Đuriš, Jelena and El-Rahmany, Mahmoud M. and Ibrić, Svetlana and Viseras, César",
year = "2020",
abstract = "The present work aimed at assessing the pharmaceutical tableting properties of some Egyptian kaolin samples belong to the Abu Zenima kaolin deposits (estimated at 120 million tons). Four representative samples were selected based on kaolinite richness and their structural order-disorder degree, and after purification, they were dried at 70 C and heated from room temperature up to 400 C (10 C/min). Mineralogy, micromorphology, microtexture, granulometry, porosimetry, moisture content, bulk and tapped density, direct and indirect flowability, and tableting characteristics are studied. Results indicated that purified kaolin samples were made up of 95–99% kaolinite, <3% illite, 1% quartz and 1% anatase. The powder showed mesoporous character (pore diameters from 2 to 38 nm and total pore volume from 0.064 to 0.136 cm3/g) with dominance of fine nanosized particles (<1 m–10 nm). The powder flow characteristics of both the ordered (Hinckley Index HI > 0.7, crystallite size D001 > 30 nm) and disordered (HI < 0.7, D001 < 30 nm) kaolinite-rich samples have been improved (Hausner ratio between 1.24 and 1.09) as their densities were influenced by thermal treatment (with some observed changes in the kaolinite XRD reflection profiles) and by moisture content (variable between 2.98% and 5.82%). The obtained tablets exhibited hardness between 33 and 44 N only from the dehydrated powders at 400 C, with elastic recovery (ER) between 21.74% and 25.61%, ejection stress (ES) between 7.85 and 11.45 MPa and tensile fracture stress (TFS) between 1.85 and 2.32 MPa, which are strongly correlated with crystallinity (HI) and flowability (HR) parameters. These findings on quality indicators showed the promising pharmaceutical tabletability of the studied Egyptian kaolin powders and the optimization factors for their manufacturability and compactability.",
publisher = "MDPI",
journal = "Minerals",
title = "Flow and tableting behaviors of some egyptian kaolin powders as potential pharmaceutical excipients",
volume = "10",
number = "1",
doi = "10.3390/min10010023"
}

Awad, M. E., López-Galindo, A., Medarević, Đ., Đuriš, J., El-Rahmany, M. M., Ibrić, S.,& Viseras, C.. (2020). Flow and tableting behaviors of some egyptian kaolin powders as potential pharmaceutical excipients. in Minerals
MDPI., 10(1).
https://doi.org/10.3390/min10010023

Awad ME, López-Galindo A, Medarević Đ, Đuriš J, El-Rahmany MM, Ibrić S, Viseras C. Flow and tableting behaviors of some egyptian kaolin powders as potential pharmaceutical excipients. in Minerals. 2020;10(1).
doi:10.3390/min10010023 .

Awad, Mahmoud E., López-Galindo, Alberto, Medarević, Đorđe, Đuriš, Jelena, El-Rahmany, Mahmoud M., Ibrić, Svetlana, Viseras, César, "Flow and tableting behaviors of some egyptian kaolin powders as potential pharmaceutical excipients" in Minerals, 10, no. 1 (2020),
https://doi.org/10.3390/min10010023 . .